This document provides an overview of REST and how to implement it with Java using frameworks like JAX-RS. It discusses REST principles like resources having identifiers and exposing a uniform interface. It shows how to define Java REST services using annotations to map HTTP methods to methods. It also covers writing custom entity providers to support different media types and handling requests, responses, and exceptions.

1. SDC 2008 REST made simple with Java

2. Niklas Gustavsson [email_address] http://protocol7.com http://twitter.com/protocol7

3. REST made simple with Java

4. REST?

5. HTTP 1.1

6. Some HTTP history

7. Some HTTP history

8. HTTP done right

10. Principles

11. Principles Everything is a resource

12. Principles A resource has an identifier http://example.com/customers/1453

13. Principles We transfer representations

14. Principles All resources expose a uniform interface GET, POST, PUT, DELETE

15. Principles Hypermedia as the engine of application state

16. Principles Client-server, Stateless, Cacheable, Layered

17. Why?

18. Why? It's easy! Well, it's not

19. Why? It's what the cool kids use

20. Why? Web has been successful, copy!

21. Why? It's what others use

22. Why? Interoperability on the right level

23. Frameworks, yeay!

24. JAX-RS (aka JSR-311)

25. Jersey http://jersey.dev.java.net Restlets http://www.restlet.org RESTeasy http://www.jboss.org/resteasy CXF http://cxf.apache.org

26. POJO based Annotation heavy

27. Resources

28. Code! Show me the code!

29. public class TimeReportService { private TimeReportDao reportDao; public TimeReport getReport(String username) { return reportDao.forUser(username); } public void saveReport(TimeReport report) { reportDao.update(report); } ... }

30. Request mapping

31. @Path("report") public class TimeReportService { private TimeReportDao reportDao; @GET public TimeReport getReport(String username) { return reportDao.forUser(username); } @PUT public void saveReport(TimeReport report) { reportDao.update(report); } ... }

33. public class TimeReportApplication extends Application { @Override public Set<Class<?>> getClasses() { Set<Class<?>> resources = new HashSet<Class<?>>(); resources.add(TimeReportService.class); return resources; } }

34. Path parameters and contexts

35. @Path(&quot;{username}/report&quot;) public class TimeReportService { @GET public TimeReport getReport(@PathParam(&quot;username&quot;) String username) { return reportDao.forUser(username); } ... } http://example.com/niklas/report

36. @GET public TimeReport getReport(@Context SecurityContext sc) { if(sc.isSecure()) { Principal user = sc.getUserPrincipal(); return reportDao.forUser(user.getName()); } else { ... throw error, redirect to login } }

37. @GET public TimeReport getReport(@CookieParam(&quot;username&quot;) String username) { return reportDao.forUser(username); }

39. Any media type is allowed XML, JSON, text/plain, Binary files, ...

40. Entity providers MessageBodyReader, MessageBodyWriter

41. Standard Entity providers

43. Writing your own Entity provider

44. BEGIN:VFREEBUSY DTSTART:20090324T080000Z DTEND:20090324T170000Z DTSTAMP:20090316T123136Z UID:ca668b14ddf589ea8650b0b992eb64a656cdbc7e@google.com SUMMARY:SDC2009 END:VFREEBUSY

45. @Provider @Produces(&quot;text/calendar&quot;) public class TimeReportICalWriter implements MessageBodyWriter<TimeReport> { public void writeTo(TimeReport t, Class<?> type, Type genericType,Annotation[] annotations,MediaType mediaType,MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) { PrintWriter wr = new PrintWriter(entityStream); ... for(TimeRange range : t.getRanges()) { wr.println(&quot;BEGIN:VFREEBUSY&quot;); wr.println(&quot;DTSTART:&quot; + DF.format(range.getStartTime())); wr.println(&quot;DTEND:&quot; + DF.format(range.getEndTime())); wr.println(&quot;SUMMARY:&quot; + range.getDescription()); wr.println(&quot;END:VFREEBUSY&quot;); } ... }

46. Response, ResponseBuilder

47. Exception Mapping

48. Deployment

49. JAX-RS limitations

50. JAX-RS limitations Lifecycle support

51. JAX-RS limitations Weak support for links, caching, method tunneling

52. JAX-RS limitations Accept based content negotiation only http://example.com/report http://example.com/report.xml http://example.com/report.cal http://example.com/report.json

53. JAX-RS limitations Limited security support

54. JAX-RS limitations Leaky abstraction

55. Try it out! And have a look at the alternatives

56. Want more?

57. Questions?

58. [email_address]

59. Attributions http://www.flickr.com/photos/psd/421186578/ http://www.flickr.com/photos/sineout/2491569707/ http://www.flickr.com/photos/apelad/sets/72157594388426362/ http://www.flickr.com/photos/goopymart/289959670